Optical switches have heretofore been provided. Many of such switches use macroscopic rotators. Switches utilizing electromagnetic motors have been disclosed to move either an input optical fiber or a refractive or reflective element interspersed between input and output optical fibers. Examples of such designs that use piezoelectric elements to move refractive or reflective elements are shown in U.S. Pat. Nos. 5,647,033 to Laughlin, U.S. Pat. No 5,748,813 to Buchin and U.S. Pat. No 5,742,712 to Pan et al. All of switches are relatively large and expensive.
A micromachined optical switch is disclosed in U.S. Pat. No. 5,446,811 to Field et al. and uses a bimetallic element to displace an optical fiber into alignment with one or more optical fibers. Such switch, however, is not easily extendable to a switch having a relatively large number of output fibers and bimetallic actuators are relatively slow.
Micromachined devices to tilt or rotate mirrors are known in the prior art, but suffer from various limitations. A one dimensional or two dimensional mirror rotator that tilts about axes in the plane of the substrate used to fabricate the device is disclosed in Dhuler et al., "A Novel Two Axis Actuator for High Speed Large Angular Rotation", Transducers '97, Vol. 1, pp. 327-330. The actuator uses a variable gap parallel plate capacitor as the drive element, which suffers from non-linear response of force or angular displacement as a function of applied voltage. A similar type of tilting mirror is described in Kruth et al., "Silicon Mirrors and Micromirror Arrays for Spatial Laser Beam Modulation", Sensors and Actuators A 66 (1998), pp. 76-82. Such mirrors are typically designed for use in projection displays or in scanners for bar code reading. A scanner using surface micromachining technology and having a mirror that is tilted out of the plane of the fabrication is described in Kiang et al., "Surface-Micromachined Electrostatic-Comb Driven Scanning Micrormirrors for Barcode Scanners", Ninth Annual Int. Workshop on Micro Electro Mechanical Systems, San Diego, 1996, pp. 192-19997. All of such devices tend to have difficulty in maintaining flatness and smoothness in the mirror elements and may have difficulty in precise static positioning of the mirror due to hysteresis in the coupling between the electrostatic comb drive actuator in the plane of the substrate and the mirror element out of the substrate plane.
In general, it is an object of the present invention to provide a relatively inexpensive optical microswitch having a small form factor.
Another object of the invention is to provide an optical microswitch of the above character in which the reflective face of a micromirror rotates in the focal plane of a focusing lens.
Another object of the invention is to provide an optical microswitch of the above character in which first and second micromirrors are closely packed and disposed in the focal plane of a focusing lens.
Another object of the invention is to provide an optical microswitch of the above character which is capable of coupling visible or infrared light into an optical fiber with low transmission losses.
Another object of the invention is to provide an optical microswitch of the above character which has relatively fast switching times.
Another object of the invention is to provide an optical microswitch of the above character in which the mirror is capable of angular rotations over a relatively large range.